Photographic processes and products employing 5-hydroxy-4-azaphenanthrenyl phthaleins as optical filter agents

ABSTRACT

This invention relates to a class of phthalein indicator dyes useful as optical filter agents in photographic processes to protect a selectively exposed photosensitive material from further exposure during processing in the presence of indicident light. Such dyes comprise 3,3-disubstituted phthalides and 3,3disubstituted naphthalides wherein the 3,3 substituents are parahydroxy polycyclic aryl radicals possessing a nitrogen atom included in the ring system adjacent to the para-hydroxy group.

United States Patent 1 Idelson Dec. 18, 1973 PHOTOGRAPHIC PROCESSES ANDPRODUCTS EMPLOYING 5-HYDROXY-4-AZAPHENANTHRENYL PHTHALEINS AS OPTICALFILTER AGENTS Inventor: Elbert M. Idelson, Newton Lower Falls, Mass.

Assignee: Polaroid Corporation, Cambridge,

Mass.

Filed: Sept. 2, 1971 Appl. No.: 177,513

US. Cl. 96/3, 96/29 D, 96/84 R,

260/326.14 Int. Cl. G03c 1/84, G03c 5/54, G030 7/00 Field of Search96/3, 29 D, 84 R References Cited UNITED STATES PATENTS 11/1972 Bloom etal. 96/3 Primal; Examiner-Norman G. Torchin Assistant Examiner-AlfonsoT. Suro Pico Attorney-Charles Mikulka et al.

[ 5 7 ABSTRACT 45 Claims, N0 Drawings PHOTOGRAPHIC PROCESSES ANDPRODUCTS EMPLOYING 5-HYDROXY-4-AZAPHENANTHRENYL PHTHALEINS AS OPTICALFILTER AGENTS BACKGROUND OF THE INVENTION 1. Field of the lnvention Thepresent invention relates to novel chemical compounds, and morespecifically, it relates to a new class of phthalein indicator dyes. Ina particular aspect it relates to certain phthaleins useful as opticalfilter agents in photographic processes for protecting an exposedphotosensitive material from post-exposure fogging during development inthe presence of extraneous incident light and to such photographic uses.

2. Description of the Prior Art A number of photographic prcesses bywhich images may be developed and viewed within seconds or minutes afterexposure have been proposed. Such processes generally employ aprocessing composition which is suitably distributed between twosheet-like elements, the desired image being carried by one of saidsheetlike elements. The resulting images may be in blackand-white, e.g.,in silver, or in one or more colors. Processing may be conducted in oroutside of a camera. The most useful of such processes are the diffusiontransfer processes which have been proposed for forming silver or dyeimages, and several of these processes have been commercialized. Suchprocesses have in common the feature that the final image is a functionof the formation of an image-wise distribution of an image-providingreagent and the diffusion transfer of said distribution to or from thestratum carrying the final image, whether positive or negative.

U.S. Pat. No. 3,415,644 discloses a composite photosensitive structure,particularly adapted for use in reflection type photographic diffusiontransfer color processes. This structure comprises a plurality ofessential layers including, in sequence, a dimensionally stable opaquelayer; one or more silver halide emulsion layers having associatedtherewith dye image-providing material which is soluble and diffusible,in alkali, at a first pH, as a function of the point-to-point degreeofits associated silver halide emulsions exposure to incident actinicradiation; a polymeric layer adapted to receive solubilized dyeimage-providing material diffusing thereto; a polymeric layer containingsufficient acidifying capacity to effect reduction of a processingcomposition from the first pH to a second pH at which the dyeimage-providing material is substantially nondiffusible; and adimensionally stable transparent layer. This structure may be exposed toincident actinic radiation and processed by interposing, intermediatethe silver halide emulsion layer and the reception layer, an alkalineprocessing composition providing the first pH and containing alight-reflecting agent, for example, titanium dioxide to provide a whitebackground. The light reflecting agent (referred to in said patent as anopacifying agent") also performs an opacifying function, i.e., it iseffective to mask the developed silver halide emulsions and also acts toprotect the photoexposed emulsions from postexposure fogging by lightpassing through the transparent layer if the photoexposed film unit isremoved from the camera before image formation is complete.

In a preferred embodiment, the composite photosensitive structureincludes a rupturable container, retaining the alkaline processingcompositon having the first pH and light-reflecting agent, fixedlypositioned extending transverse a leading edge of the compositestructure in order to effect, upon application of compressive pressureto the container, discharge of the processing composition intermediatethe opposed surfaces of the reception layer and the next adjacent silverhalide emulsion.

The liquid processing composition distributed intermediate the receptionlayer and the silver halide emulsion, permeates the silver halideemulsion layers of the composite photosensitive structure to initiatedevelopment of the latent images contained therein resultant fromphotoexposure. As a consequence of the development of the latent images,dye image-providing material associated with each of the respectivesilver halide emulsion layers is individually immobilized as a functionof the point-to-point degree of the respective silver halide emulsionlayer photoexposure, resulting in imagewise distributions of mobile dyeimage-providing materials adapted to transfer, by diffusion, to thereception layer to provide the desired transfer dye image. Subsequent tosubstantial dye image formation in the reception layer, a sufficientportion of the ions of the alkaline processing composition transfers, bydiffusion, to the polymeric neutralizing layer to effect reduction inthe alkalinity of the composite film unit to the second pH at which dyeimage-providing material is substantially nondiffusible, and further dyeimageproviding material transfer is thereby substantially obviated.

The transfer dye image is viewed, as a reflection image, through thedimensionally stable transparent layer against the background providedby the reflecting agent, distributed as a component of the processingcomposition, intermediate the reception layer and next adjacent silverhalide emulsion layer. The thus-formed stratum effectively masksresidual dye image-providing material retained in association with thedeveloped silver halide emulsion layer subsequent to processing.

In the copending U.S. Pat. application Ser. No. 786,352 of Edwin H.Land, filed Dec. 23, 1968, now abandoned, and Ser. No. 101,968 filedDec. 28, 1970, now U.S. Pat. No. 3,647,437, in part a continuation ofSer. No. 786,352, an organic light-absorbing reagent (or optical filteragent), such as a dye, which is present at a light-absorbing species atthe first pH and which may be converted to a substantiallynon-light-absorbing species at the second pH is used in conjunction withthe light-reflecting agent to protect the selectively exposed silverhalide emulsions from post-exposure fogging when development of thephotoexposed emulsions is conducted in the presence of extraneousincident actinic radiation impinging on the transparent layer of thefilm unit. When such a dye is employed, it is preferred that the dyeselected possess a relatively high pKa so that it will be in alight-absorbing form during the initial stages of processing, and alsocapable of being rendered substantially non-light absorbing within arelatively brief interval as the pH subsequent to substantial imageformation is reduced.

Copending U.S. Pat. application Ser. No. 103,392 filed Jan. 4, 1971, nowU.S. Pat. No. 3,702,245, discloses various pH-sensitive dyes derivedfrom certain hydroxy-substituted carbocyclic aryl compounds, viz.,particular phenols and naphthols which due to their high pKa andspectral absorption characteristics are useful as optical filter agentsfor absorbing incident radiation actinic to selectively exposedphotosensitive materials within a predetermined wavelength range in thelonger wavelength region of the visible spectrum. Among the dyesdisclosed therein are phenol and lnaphthol phthaleins wherein thep-hydroxyphenyl or p-hydroxynaphthyl radicals are substituted with ahydrogen-bonding group on a carbon atom adjacent to the functionalhydroxy group to raise the pKa. These phenol and l-naphthol phthaleinsform the subject matter of copending US. Pat. applications Ser. Nos.103,864 and 103,865, respectively both filed Jan. 4, 1971.

The association of two atoms through hydrogen to form a hydrogen bondbetween or within molecules is well known. When hydrogen is attached toan electronegative atom, for example, or N, the resultant bond ispolarized. If directed toward another atom (M) with an unshared pair ofelectrons, the hydrogen acts as a bridge between the atoms (0-H M) dueto the electrostatic attraction to both atoms between which the hydrogenproton can be transferred. In the phenol and naphthol phthaleins of thetwo aforementioned applications, an intramolecular hydrogen bond isformed between the p-hydroxy group and the hydrogen-bonding groupsubstituted on an adjacent carbon atom.

The present invention is concerned with another class of phthaleinindicator dyes possessing a high pKa which dyes also are among thosedisclosed as optical filter agents in aforementioned application Ser.No. 103,392.

SUMMARY OF THE INVENTION It is therefore the primary object of thepresent invention to provide a novel class of phthalein indicator dyes.

It is another object of the present invention to provide products,compositions and processes for the development of photosensitivematerials in which the novel phthalein indicator dyes are used.

Other objects of this invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises the processes involving the severalsteps and the relation and order of one or more of such steps withrespect to each of the others, and the products and compositionspossessing the features, properties and the relation of elements whichare exemplified in the following detailed disclosure, and the scope ofthe application of which will be indicated in the claims.

According to the present invention, there is provided a novel class ofphthalein indicator dyes derived from certain hydroxy-substitutedpolycyclic aryl compounds having a nitrogen atom included in the ringsystem as exemplified by 5-hydroxy-4-azaphenanthrene. These dyes includeboth phthalides and naphthalides and will be defined with greaterparticularity hereinafter.

The indicator dyes of the present invention, like phthalein indicators,in general, possess spectral absorption characteristics which arereversibly alterable in response to changes in environmental pH. Thesedyes possess a highly colored form capable of absorbing visibleradiation in alkaline media at a first pH value above their respectivepKa and a substantially colorless form, i.e., a form which issubstantially non-lightabsorbing in the visible spectrum in lessalkaline media at a second pH value below their resepctive pKa. By

pKa is meant the pH at which about 50 percent of the dye is present inits light-absorbing form and about 50 percent is present in itsnon-light-absorbing form.

It will be appreciated that such compounds will find utility intitrations and other analytical procedures where phthalein indicatordyes are commonly employed, for example, to measure changes in pH valueas reflected by the change in color of the dye from one color to anotheror from colored to colorless or vice versa. The indicator dyes of thepresent invention, however, compared to conventional phthaleins ofhydroxysubstituted compounds, such as, simple phenol phthalein andl-naphthol phthalein possess a higher pKa which render them useful asoptical filter agents in photographic processes performed under alkalineconditions, and especially in photographic processes employing highlyalkaline media.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description.

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the presentinvention, it has been found that phthalein indicator dyes having a highpKa may be obtained without adding substituents, i.e., without having tosubstitute hydrogen-bonding groups on the phydroxy radicals of the dye.This may be achieved by utilizing hydroxy-substituted polycyclic arylcompounds having a nitrogen atom included in the ring'systern, providedthe nitrogen atom is in a position to give a group,

OH N: 0H HN-- HAA A6 As compared to phenol and l-naphthol compoundscontaining a cyclic substituent subject to rotation, such hydrogenbonding is particularly effective in the compounds of the presentinvention since the N atom of the polycyclic molecule is in fixedposition relative to the functional hydroxy group. Besides the increasein pKa resulting from the hydrogen bond thus formed, these dyes arecapable of absorbing radiation over a relatively broad wavelength rangein the visible spectrum. Because of their spectral absorptioncharacteristics and because they are colored at a comparatively high pH,they are especially useful as optical filter agents in photographicprocesses conducted under highly alkaline conditions for affordingprotection of a selectively exposed photosensitive material fromincident actinic radiation in the visible spectrum.

The indicator dyes of the present invention may be defined as phthaleinsselected from 3,3-disubstituted phthalides and 3,3-disubstitutednaphthalides wherein the 3,3 substituents are polycyclic aryl radicalscontaining the group,

OH N: on HN- said radicals being bonded to the phthalide or naphthalideby a carbon atom para to the OH of said group. Illustrative of theaforementioned groups are wherein Y and Y, the same, represent the atomsnecessary to complete a ring having 5 or 6 members; Z and Z, the same,represent the atoms necessary to complete a ring system having at least5 members and X represents the atoms necessary to complete a ringclosingmoiety selected from a phthalide and a naph thalide.

The indicator dyes defined above and as represented in the aforegoingformula may contain substituents on the polycyclic aryl radicals and/orring-closing moiety as may be desired which do not interfere with thefunction of the dye for its selected ultimate use. Where it is desiredthat the indicator dye be substantially immobile or non-diffusible inthe processing solution, it may be substituted with a bulky group, suchas, a long chain substituent, e.g., dodecyloxy, hexadecyl ordodecylphenyl. Also, it may be substituted with solubilizing groups,e.g., carboxy or sulfo to adjust the solubility in a given solution.Because of the convenience in preparation, the dyes of the presentinvention preferably are symmetrical, i.e., bis phthalides and bisnaphthalides wherein the two polycyclic aryl radicals are the same,i.e., they contain the same substituents in the same position.

Typical substituents include branched or straight chain alkyl, such as,methyl, ethyl, isopropyl, n-butyl, t-butyl, hexyl, octyl, dodecyl,hexadecyl, octadecyl and eicosanyl; aryl, such as, phenyl,Z-hydroxyphenyl, and naphthyl; alkaryl, such as, benzyl, phenethyl,phenylhexyl, p-octylphenyl, p-dodecylphenyl; alkoxy, such as, methoxy,ethoxy, butoxy, l-ethoxy-2-(B- ethoxyethoxy), dodecyloxy andoctadecyloxy; aryloxy,

such as phenoxy, benzyloxy, naphthoxy; alkoxyalkyl, such asmethoxyethyl, dodecyloxyethyl; halo such as, fluoro, bromo, and chloro;trifluoralkyl. such as. trifluoromethyl, monoand bistrifluoromethylcarbinol:

sulfonamido; sulfamoyl; acyl and its derivatives, aminomethyl; amido;sulfonyl; sulfo; cyano; nitro; amino including mono-and disubstitutedamino, e.g., N-ethyl amino and N,N'dimethylamino; carboxy; and hydroxyl.Specific examples of indicator dyes within the scope of the presentinvention are as follows:

N ll 1 9 I l \l/\ /V x COOH N N l I HO OH l n-CuH:5 l I Il-C11Hg5 O l=o(boot! N N l l P l SO;H HO;S

N N l a i l \/[l( Q 0 The phthalic or naphthalic acid reagent selectedto ultimately form the ring-closing moiety may be the acid, the acidanhydride or the acid chloride. The terms phthalic acid reagent" andnaphthalic acid reagent" as used herein are intended to include thecorresponding anhydrides and acid chlorides. These reagents may besubstituted, with solubilizing groups. such as, carboxy, e.g.,hemimellitic acid; with long chain substituents to adjust the mobilityof the final dye, c.g., sulfonamido containing a long chain alkyl group(N- H--SO -nC, H or with other substituents as may be desired.

Another method of preparing these phthalein indicator dyes comprisesreacting the selected hydroxysubstituted polycyclic aryl compound withphthalaldehydic or naphthalaldehydic acid, which acids may containsubstituents in the presence of a mild acid catalyst to yield thecorresponding (na)phthalidyl-substituted intermediate which is thenoxidized by treating with dichlorodicyanoquinone or other suitableoxidizing agent. The oxidized intermediate is then reacted with anothermole of polycyclic aryl compound to yield the desired dye. This methodof preparing certain phthalein indicator dyes forms the subject matterof copending US. Pat. application Ser. No. 108,662 filed Jan. 21, 1971.

As noted above, the hydroxy-substituted polycyclic aryl compounds usedas the starting materials in these methods contain the group,

0H N: OH HN- Illustrative compounds include:

N /JA It will be appreciated that the aryl compounds used as thestarting material may contain substituents as may be desired in thecomplete dye, provided the carbon atom para to the hydroxy group isunsubstituted and thus, available for reaction with the selected acid.If desired, substituents may be substituted on the completed dye, e.g.,SO H groups.

The following Examples are given to further illustrate the presentinvention and are not intended to limit the scope thereof.

EXAMPLE 1 Preparation of the compound of Formula (1):

19.5 grams of 5-hydroxy-4-azaphenanthrene was dissolved in 60 ml. ofnitromethane, in a flame dried, three-neck flask under dry (P nitrogenwith stirring. To this light yellow solution was added 8 grams of freshaluminum chloride in small portions. The solution turned more orange andsome precipitation took place. To this solution was added 2.105 grams ofhemimellitic anhydride acid chloride; the solution turned a reddishorange. 20 ml. of nitrobenzene was then added, and the solution washeated with stirring on an oil bath at 40C. After 6 hours, the solutionturned greenish in color. To this solution was added an additional 1.95grams of 5-hydroxy-4-azaphenantrene, the reaction was then heated at60C. with stirring for one hour. An emerald green color developed. Tothis solution, 0.72 ml. of acetic anhydride was slowly added, dropwise;the reaction was heated at 60C. with stirring for 48 hours. The reactionwas followed by T. L. C. [chloroform/methanol 1:1 on silica gel].Indicator was detected with 5 percent sodium hydroxide in 20 percentaqueous ethanol. The reaction mixture was then poured into ice 100 g.)with stirring and 100 ml. of5 percent hydrochloric acid was added. Theflask was washed with methanol and the methanol combined with the watersolution. The solution was then steam distilled for 4 hours to removethe methanol, nitromethane, and nitrobenzene. The aqueous solution wasthen filtered. The residue solid by T. L. C. was largely product 80percent by weight). The filtrate contained only a small amount ofindicator. The solid was dissolved in methylene chloride and evaporatedonto silica gel. This was then eluted on a silica gel'column withchloroform and percent aqueous methanol to yield the indicator dye. Someof the indicator became absorbed on the column. This was soxletextracted with chloroform for 24 hours. Total yield of the titlecompound was 1.05 grams as a light yellow solid.

EXAMPLE 2 Preparation of the compound of formula (3):

Fl l (h In a ml. three-neck flask under nitrogen 1 g. of the product ofExample 1 above was dissolved in small portions into 50 ml. of 20percent fuming sulfuric acid with stirring. The reaction solution turneda very dark emerald green. After 2 hours of stirring at room temperatureT. L. C. [methanol/chloroform on silica gel] showed no startingmaterial. The solution was then carefully poured onto 200 g. of ice andthe flask washed with 100 ml. of water. The aqueous solution wasfiltered to give a yellow solid which was slurried with a small amountof methanol, filtered and dried to yield 670 mg. of the title compound.An additional 200 mg. of product precipitated from the aqueous solutionovernight. Melting point C. (dec.).

The 5-hydroxy-4-azaphenanthrene used in Example 1 above was prepared inaccordance with the procedure described in Helv. Chem. Acta, Vol. 27, p.1461 (1944).

As noted above, the indicator dyes of the present invention have arelatively high pKa as compared to conventional phthaleins ofhydroxy-substituted compounds, such as, phenol and l-naphtholphthaleins. For example, the pKa values measured for the indicator dyesof Examples 1 and 2 were 13.8 and 13.9, respectively. in comparison,l-naphtholphthalein has two pKas, one at about 7 and a second at about8. Phenol phthalein and phenol 7-carboxy phthalein both have pKas ofabout 9.6.

The pH sensitive indicator dyes of the present invention may be used asoptical filter agents in any photographic process including conventionaltray processing and diffusion transfer photographic techniques. In suchprocesses, the dye or dyes during development of a selectively exposedphotosensitive material will be in a position and in a concentrationeffective to absorb a given level of non-selective radiation incident onand actinic to the photosensitive material. The dyes may be initiallydisposed in the film unit, for example, in a layer(s) coextensive withone or both surfaces of the photosensitive layer. Where selectiveexposure of the photosensitive material is made through a layercontaining the indicator dye, then the dyes should be in anon-light-absorbing form until the processing solution is applied.Alternately, the dyes may be initially disposed in the processingcomposition in their lightabsorbing form, for example, in the developingbath in tray processing on in the layer of processing solutiondistributed between the photosensitive element and the superposedimage-receiving element (or spreader sheet) in diffusion transferprocessing. The particular indicator dye or dyes selected should have anabsorption spectrum corresponding to the sensitivity of thephotosensitive layer, so as to afford protection over the predeterminedwavelength range required by the particular photosensitive materialemployed and should have a pka such that they are in their colored form,i.e.,

light-absorbing form at the pH at which the photo-' graphic process isperformed. Most commercially useful photographic processes are performedunder alkaline conditions. Diffusion transfer processes, for example,usually employ highly alkaline processing solutions having a pH inexcess of 12.

In photographic processes where the optical filter agent is retained ina stratum through which the final image is to be viewed, the color ofthe indicator dye may be discharged subsequent to image formation byadjusting the pH of the system to a value at which the dye issubstantially non-light absorbing in the visible spectrum. Inphotographic processes performed at an alkaline pH, the optical filteragent, such as, a dye or dyes of the present invention are renderedsubstantially colorless by reducing the environmental pH. In processeswhere the optical filter agent is removed or separated from the layercontaining the final image or retained in a layer that does notinterfere with viewing of the final image, it is unnecessary to convertthe indicator dye to its non-light-absorbing form, though the color maybe discharged if desired.

The concentration of indicator dye is selected to provide the opticaltransmission density required, in combination with other layersintermediate the silver halide emulsion layer(s) and the incidentradiation, to prevent nonimagewise exposure, i.e., fogging, by incidentactinic light during the performance of the particular photographicprocess. It has been found, by interposing neutral density (carboncontaining) filters over a layer of titanium dioxide, that atransmission density of approximately 6.0 from said neutral densityfilters was effective to prevent fogging of a diffusion transfermulticolor film unit of the type described in said US. Pat. No.3,415,644 having a transparent support layer and an Equivalent ASAExposure Index of approximately 75, when processed for one minute in10,000 foot candles of color corrected light, a light intensityapproximating the intensity of a noon summer sun. The transmissiondensity required to protect such a film unit under the stated conditionsmay also be expressed in terms of the system" transmission density ofall the layers intermediate the silver halide layer(s) and the incidentlight; the system transmission density required to protect color filmunits of the aforementioned type and photographic speed has been foundto be on the order of 7.0 to 7.2. Lesser levels of optical transmissiondensity would, of course, provide effective protection for shorterprocessing times, lesser light intensities and/or films having lowerexposure indices. The transmission density and the indicator dyeconcentration necessary to provide the requisite protection fromincident light may be readily determined for any photographic process byfollowing the above described procedure or obvious modificationsthereof.

Since most commercial photographic processes employ photosensitivematerials sensitive to and exposable by actinic radiation throughout thevisible spectrum, e.g., black-and-white panchromatic silver halideemulsions and multilayer silver halide emulsion elements, it ispreferred to use a second dye(s) in conjunction with the subject dye(s)that has a principal absorption in a second and at least partiallydifferent predetermined wavelength range such that the combination ofdyes will afford protection from non-selective incident actinicradiation over the range of 400 to 700 nm. The second dye employed maybe non-color-changing but preferably, is also pH sensitive, i.e., hasreversibly alterable spectral absorption characteristics in response tochanges in the environmental pH so that it may be renderedlight-absorbing or non-light-absorbing as desired. Illustrative of suchdyes are phthaleins derived from indoles, such as, indole phthalein. Thesecond dye also may be initially present in the film unit or in theprocessing composition as discussed above either together with orseparate from the subject dyes and subsequent to processing may beremoved from the film unit or retained within the film structure,provided it is in a form or position such that it does not interferewith viewing of the image produced.

The dyes of the present invention are especially useful as opticalfilter agents in diffusion transfer processes, for example, thoseemploying composite diffusion transfer photosensitive elements includinga film pack or roll wherein superposed photosensitive andimage-receiving elements are maintained as a laminate after formation ofthe final image. Such elements include at least one transparent supportto allow viewing of the final image without destroying the structuralintegrity of the film unit. Preferably, the support carrying thephotosensitive layer(s) is opaque and the support carrying theimage-receiving layer is transparent and selective photoexposure of thephotosensitive layer(s) and viewing of the final image both are effectedthrough the latter support. The final image is viewed as a reflectionprint, i.e., by reflected light, provided by a reflecting agentinitially disposed in the processing composition applied and maintainedintermediate the image-receiving and next adjacent photosensitive layeror by a preformed layer of reflecting agent initially positionedintermediate the image-receiving and next adjacent photosensitive layer.It will be understood that a preformed reflecting layer, while it shouldbe capable of masking the photosensitive layer(s) subsequent to imageformation, should not interfere with selective photoexposure of thephotosensitive material prior to processing.

When utilizing reflection-type composite film units, the indicator dyeor dyes employed as the optical filter agent(s) may be positionedinitially in a layer of the film unit, e.g., in a layer between theimage-receiving and next adjacent photosensitive layer through whichphotoexposure is effected provided it is incorporated under conditions,i.e., at a pH such that it will not absorb actinic radiation intended toselectively expose the photosensitive material to form a latent imagetherein. For example, the optical filter agent may be in a layer coatedover either the image-receiving layer or the next adjacentphotosensitive layer and should remain substantially non-light-absorbinguntil a processing composition is applied providing a pH at which theindicator dye is capable of being rapidly converted to itslightabsorbing form to provide light protection when the film unit isremoved from the camera. Rather than being initially disposed in thefilm unit, the indicator dye may be initially present in the processingcomposition applied intermediate the image-receiving and next 4 adjacentphotosensitive layer subsequent to photoexposure. The dye, wheninitially disposed in the processing composition, will be in itslight-absorbing form.

The dyes selected as optical filter agents should exhibit at the initialpH of the processing, maximum spectral absorption of radiation at thewavelengths to which the film units photosensitive silver halide layeror layers are sensitive, and preferably, should be substantiallyimmobile or non-diffusible in the alkaline processing composition inorder to achieve optimum efficiency as a radiation filter and to preventdiffusion of filter agent into layers of the film unit where itspresence may be undesirable. Recognizing that the filter agentabsorption will detract from image-viewing characteristics bycontaminating reflecting pigment background, the selected agents shouldbe those exhibiting major spectral absorption at the pH at whichprocessing is effected and minimal absorption at a pH below that whichobtains during transfer image formation. Accordingly, the selectedoptical filter agent or agents should possess a pKa below that of theprocessing pH and above that of the environmental pH subsequent totransfer image formation.

As discussed previously, the concentration of indicator dye is selectedto provide the optical transmission density required, in combinationwith other layers intermediate the silver halide emulsion layer(s) andthe incident radiation, to prevent nonimagewise exposure, i.e., fogging,by incident actinic light during the performance of the particularphotographic process. In the processes where the indicator dye or dyesselected as optical filter agents are used in conjunction with areflecting agent or agents, the optical filter agents and reflectingagents together should possess the optical transmission densitynecessary to protect the photosensitive material for the particularphotographic process. The optimum concentration of optical filteragent(s) or filter agent(s) together with reflecting agent(s) may bereadily determined empirically for each photographic system.

While substantially any reflecting agent may be employed for the layerof reflecting agent, either preformed or applied as a component of theprocessing composition, it is preferred to select an agent that will notinterfere with the color integrity of the dye transfer image, as viewedby the observer, and, most preferably, an agent which is aestheticallypleasing to the viewer and does not provide a background detracting fromthe information content of the image. Particularly desirable reflectingagents will be those providing a white background, for viewing thetransfer image, and specifically those conventionally employed toprovide background for reflection photographic prints and, especially,those agents possessing the optical properties desired for reflection ofincident radiation.

As examples of reflecting agents, mention may be made of barium sulfate,zinc sulfide, titanium dioxide, barium stearate, silver flake,silicates, alumina, zirconium oxide, zirconium acetyl acetate, sodiumzirconium sulfate, kaolin mica, and the like.

Illustrative of the photographic use of the indicator dyes of thepresent invention as optical filter agents, a photographic film unit maybe prepared by coating, in succession, on a gelatin subbed, 4 mil.opaque polyethylene terephthalate film base, the following layers:

1. a layer of the cyan dye developer 1,4-bis-(,B-[hydroquinonyl-a-methyl]-ethy1amino)-5,8-dihydroxyanthraquinonedispersed in gelatin and coated at a cov erage of about 80 mgs./ft. ofdye and about 100 mgs./ft of gelatin;

2. a red-sensitive gelatino-silver iodobromide emulsion coated at acoverage of about 225 mgs./ft. of silver and about 50 mgs./ft. ofgelatin;

3. a layer of the acrylic latex sold by Rohm and Haas Co., Philadelphia,Pa., U.S.A., under the trade designation AC-61 and polyacrylamide coatedat a coverage of about 150 mgs./ft. of AC-61 and about 5 mgs./ft. ofpolyacrylamide;

4. a layer of the magenta dye developer 2-(p-[B-hydroquinonylethyl]-phenylazo)-4-isopropoxy-1- naphthol dispersed ingelatin and coated at a coverage of 70 mgs./ft. of dye and about 120mgs./ft. of gelatin;

5. a green-sensitive gelatino-silver iodobromide emulsion coated at acoverage of about 120 mgs./ft. of silver and 60 mgs./ft. of gelatin;

6. a layer comprising the acrylic latex sold by Rohm and Haas Co. underthe trade designation B-15 and polyacrylamide coated at a coverage ofabout 100 mgs- ./ft. of 8-15 and about 10 mgsjft. of polyacrylamide;

7. a layer of the yellow dye developer 4-(p-[B-hydroquinonylethyl]-phenylazo)-3-(N-n-hexylcarboxamido)-l-phenyl-S-pyrazoloneand the auxiliary developer 4'-methylphenyl hydroquinone dispersed ingelatin and coated at a coverage of about 50 mgs./ft. of dye, about 15mgs./ft. of auxiliary developer and 50 mgs./ft. of gelatin;

8. a blue-sensitive gelatino-silver iodobromide emulsion coated at acoverage of about mgs./ft. of silver and about 75 mgs./ft. of gelatin;and

9. a layer of gelatin coated at a coverage of about 50 mgs./ft. ofgelatin.

Then a transparent 4 mil. polyethylene terephthalate film base may becoated, in succession, with the following illustrative layers:

1. a 7:3 mixture, by weight, of polyethylene/maleic acid copolymer andpolyvinyl alcohol at a coverage of about 1400 mgs./ft. to provide apolymeric acid layer;

2. a graft copolymer of acrylamide and diacetone acrylamide on apolyvinyl alcohol backbone in a molar ratio of 1:3.2:1 at a coverage ofabout 800 mgs./ft. to provide a polymeric spacer layer; and

3. a 2:1 mixture, by weight, of polyvinyl alcohol andpoly-4-vinylpyridine, at a coverage of about 900 mgs./ft. and includingabout 20 mgs./ft. phenyl mercapto tetrazole, to provide a polymericimage-receiving layer.

The two components thus prepared may then be taped together in laminateform, at their respective edges, by means ofa pressure-sensitive bindingtape extending around, in Contact with, and over the edges of theresultant laminate.

A rupturable container comprising an outer layer of lead foil and aninner liner or layer of polyvinyl chloride retaining an aqueous alkalineprocessing solution comprising:

Water cc.

Potassium hydroxide 11.2 gms.

Hydroxyethyl cellulose (high viscosity) [commercially available fromHercules Powder Co., Wilmington, Delaware, under the trade name Natrasol250 3.4 gms.

N-phenethyl-a-picolinium bromide 2.7 gms.

Benzotriazole 1.15 gms.

Titanium dioxide 50.0 gms.

Il-CuHu-O may then be fixedly mounted on the leading edge of each of thelaminates, by pressure-sensitive tapes interconnecting the respectivecontainers and laminates, such that, upon application of compressivepressure to a container, its contents may be distributed, upon ruptureof the containers marginal seal, between the polymeric image-receivinglayer and next adjacent gelatin layer.

The photosensitive composite film units may be exposed through stepwedges to selectively filter radiation incident on the transparentpolyethylene terephthalate layer and processed by passage of the exposedfilm units through appropriate pressure-applying members, such assuitably gapped, opposed rolls, to effect rupture of the container anddistribution of its contents. During processing, the multicolor dyetransfer image formation may be viewed through the transparentpolyethylene terephthalate layer against the titanium dioxide backgroundprovided by distribution of the pigment containing processingcomposition between the polymeric imagereceiving layer and gelatin layer9 of the photosensitive component. The film unit may be exposed toincident light and the formation of the image may be viewed upondistribution of the processing composition by reason of the protectionagainst incident radiation afforded the photosensitive silver halideemulsion' layers by the optical filter agents and by reason of theeffective reflective background afforded by the titanium dioxide.

The spectral absorption characteristics of the indicator dye prepared inExample 1 above are graphically illustrated in FIG. 13 of theaforementioned copending application Ser. No. 103,392 which graphrepresents the optical transmission density, i.e., absorbance of the dyemeasured on a logarithm scale over the wavelength range of 350 nm. to750 nm. in aqueous alkaline solution at a pH substantially above itspKa.

The film unit detailed above is similar to that shown in FIG. 2 andrelated FIGS. 3-4 of aforementioned copending U. S. Pat. applicationSer. No. 101,968. The negative component of the film unit including thephotosensitive strata and associated dye-image-forming material; thepositive component including the timing, neutralizing and dyeablelayers; and the processing composition including its components, suchas, the alkaline material and various addenda are described in detail inapplication Ser. No. 101,968. For convenience, the specification of thisapplication is specifcally incorporated herein.

Besides the above photosensitive element, the dyes of the presentinvention may be employed in composite photosensitive elements, ingeneral, where the dyeable stratum along with any associated layers maybe contained together with the photosensitive strata as a unitary filmunit which may be termed an integral negative-positive film unitcomprising a negative component including the aforementioned essentiallayers and a positive component including at least the dyeable stratumin which the color transfer image is to be formed. The essential layersare preferably contained on a transparent dimensionally stable layer orsupport member positioned closest to the dyeable stratum so that theresulting transfer image is viewable through this transparent layer.Most preferably another dimensionally stable layer which may betransparent or opaque is positioned on the opposed surface of theessential layers so that the aforementioned essential layers aresandwiched or confined between a pair of dimensionally stable layers orsupport members, at least one of which is transparent to permit viewingtherethrough ofa color transfer image obtained as a function ofdevelopment of the exposed film unit in accordance with the known colordiffusion transfer processes. It will be appreciated that all of thesefilm units, like the specific one detailed above, may optionally containother layers performing specific desired functions, e.g., spacer layers,pH-reducing layers, etc.

Examples of such integral negative-positive film units for preparingcolor transfer images viewable without separation are those describedand claimed in aforementioned U. S. Pat. No. 3,415,644 and in U. S. Pat.Nos. 3,415,645, 3,415,646, 3,473,925, and 3,573,043.

In general, the film units of the foregoing description, e.g., thosedescribed in the aforementioned patents and/or copending applications,are exposed to form a developable image and thereafter developed byapplying the appropriate processing composition to develop exposedsilver halide and to form, as a function of development, an imagewisedistribution of diffusible dye image-providing material which istransferred, at least in part by diffusion, to the dyeable stratum toimpart thereto the desired color transfer image, e.g., a positive colortransfer image. Common to all of these systems is the provision of areflecting layer between the dyeable stratum and the photosensitivestrata to mask effectively the latter and to provide a background forviewing the color image contained in the dyeable stratum, whereby thisimage is viewable without separation, from the other layers or elementsof the film unit. As discussed previously, in some embodiments thisreflecting layer is provided prior to photoexposure, e.g., as apreformed layer included in the essential layers of the laminarstructure comprising the film unit, and in others it is provided at sometime thereafter, e.g., by including a suitable light-reflecting agent,for example, a white pigment, such as, titanium dioxide, in theprocessing composition. As an example of such a preformed layer, mentionmay be made of that disclosed in the copending applications of Edwin H.Land, Ser. Nos. 846,441, filed July 31, 1969, and 3,645, filed Jan. 19,1970 and now U. S. Pat. Nos. 3,615,421 and 3,620,724, respectively. Thereflecting pigment may be generated in situ as is disclosed in thecopending applications of Edwin H. Land, Ser. Nos. 43,741 and 43,742,both filed June 5, 1970 and now U. S. Pat. Nos. 3,647,434 and 3,647,435,respectively. In a particularly preferred form, such film units areemployed in conjunction with a rupturable container, such as, that usedabove, containing the processing composition having the light-reflectingagent incorporated therein which container is adapted upon applicationof pressure of distributing its contents to develop the exposed filmunit and to provide the light-reflecting layer.

As noted previously, the photographic use of the dyes of the presentinvention as optical filter agents to prevent post-exposure fogging of aselectively exposed photosensitive material is not limited to diffusiontransfer processes nor to such processes employing compositephotosensitive elements. While the use of such dyes in compositemulticolor diffusion transfer film units is a particularly preferredembodiment of the present invention, these dyes may be used with equallyeffective results in any photographic process where it is desired toprotect a photosensitive material from incident radiation actinic to thephotosensitive material within the wavelength range capable of beingabsorbed by the dye. For example, the subject dyes may be used inconventional tray photographic processing as a component of theprocessing bath, or they may be present in a layer coextensive with oneor both surfaces ofa layer of photosensitive material to be processedusing conventional tray procedures, provided that they arenon-lightabsorbing prior to photoexposure and also subsequent todeveloping the latent image unless the layer containing the dye is to beremoved subsequent to processing. In such procedures, the photoexposedphotosensitive material will, of course, be transferred from the camerato the processing bath in the absence of radiation actinic to thematerial.

The subject dyes also may be employed in diffusion transfer processeswhere the photosensitive and imagereceiving elements are separatedsubsequent to the formation of a transfer image or where a spreadersheet is separated from the photosensitive element to reveal a finalimage in the negative. In addition to the composite diffusion transferstructures described above, the subject dyes may be used with compositediffusion transfer film units where the final image is to be viewed bytransmitted light. Also they may be used in composite film unitsspecifically adapted, for example, for forming a silver transfer image,for developing a negative silver image by monobath processing, forobtaining an additive color image, and for obtaining a dye image by thesilver dye bleach process which structures are described in detail inaforementioned copending U. S. application Ser. No. 101,968,particularly with reference to FIGS. to 13 of the applications drawings.

Although the invention has been discussed in detail throughout employingdye developers, the preferred image-providing materials, it will bereadily recognized that other, less preferred, image-providing materialsmay be substituted in replacement of the preferred dye developers in thepractice of the invention. For example, there may be employed dyeimage-forming materials such as those disclosed in U. S. Pat. Nos.2,647,049;

2,661,293; 2,698,244; 2,698,798; 2,802,735; 3,148,062; 3,227,550;3,227,551; 3,227,552; 3,227,554; 3,243,294; 3,330,655; 3,347,671;3,352,672; 3,364,022; 3,443,939; 3,443,940; 3,443,941; 3,443,943; etc.,wherein color diffusion transfer processes are described which employcolor coupling techniques comprising, at least in part, reacting one ormore color developing agents and one or more color formers or couplersto provide a dye transfer image to a superposed image-receiving layerand those disclosed in U. S. Pat. No. 2,774,668 and 3,087,817, whereincolor diffusion transfer processes are described which employ theimagewise differential transfer of complete dyes by the mechanismstherein described to provide a transfer dye image to a contiguousimage-receiving layer, and thus including the employment ofimage-providing materials in whole or in part initially insoluble ornondiffusible as disposed in the film unit which diffuse duringprocessing as a direct or indirect function of exposure.

In view of the foregoing, it will be readily apparent that the subjectdyes are useful generally in photographic processes for producingsilver, monochromatic and multi-color images using any photosensitivematerial including conventional and direct positive silver halideemulsions. Depending upon the selected photosensitive material, one ormore of the dyes may be used alone or in combination with anotheroptical filter agent, such as another light-absorbing dye, which seconddye may be non-color-changing or another pH sensitive dye. If theselected dye or dyes do not possess the desired stability in theprocessing composition for long term storage therein, they may beinitially disposed in the film structure or stored in adouble-compartmented pod or in one of two associated pods separate fromthe processing solution until such time as the pod(s) are rupturedwhereupon the dyes are admixed with the processing solution.

Since certain changes may be made in the above product and processwithout departing from the scope of the invention herein involved, it isintended that all matter contained in the above description shall beinterpreted as illustrative and not in a limiting sense.

What is claimed:

1. A photographic process comprising the steps of selectively exposing aphotosensitive element comprising a layer of photosensitive material toradiation actinic thereto to provide a latent image therein, applying aprocessing composition to provide an indicator dye in a form capable ofabsorbing a predetermined wavelength range of radiation actinic to saidphotosensitive material, and developing said latent image while exposingsaid photosensitive element non-selectively to incident actinicradiation within said predetermined wavelength range, said indicator dyebeing present during development in a position and quantity effective toabsorb said wavelength range of incident radiation in an amountsufficient to prevent any substantial increase, as a result ofperforming said process in the presence of incident radiation withinsaid wavelength range, in the minimum density of the image obtained bysaid development of said latent image, and being selected from a3,3-disubstituted phthalide and a 3,3- disubstituted naphthalide whereinthe 3,3 substituents said radicals being bonded to saidphthalide ornaphthalide by a carbon atom para to the OH of said group.

2. A process as defined in claim 1 wherein said indicator dye isinitially disposed in said processing composition having a pH at whichsaid indicator dye is lightabsorbing, said processing composition beingapplied to said photosensitive layer and said composition containingsaid indicator dye being separated from the photosensitive layersubsequent to substantial image development.

3. A process as defined in claim 1 wherein said indicator dye isretained in said element and is rendered ineffective to prevent viewingof the final image subsequent to substantial image development byadjusting the pH of said indicator dyes environment to a value at whichit is substantially non-light-absorbing.

4. A process as defined in claim 3 wherein said indicator dye isinitially present in a processing composition permeable layer at a pHvalue at which it is substantially non-light absorbing, said layer beingcoextensive with at least one surface of said photosensitive layer andsaid processing composition applied thereto having a pH at which saidindicator dye is lightabsorbing.

5. A process as defined in claim 1 wherein said layer of photosensitivematerial is a silver halide layer.

6. A process as defined in claim 1 wherein said radicals of saidindicator dye contain the group- OH N:

7. A process as defined in claim 6 wherein said radicals are5-hydroxy-4-azaphenanthren-8-yl.

8. A process as defined in claim 7 Wehrein said dye is a phthalide.

9. A process as defined in claim 1 wherein said indicator dye isdi-(5-hydroxy-4-azaphenanthren-8-yl)7- carboxyphthalide.

10. A process as defined in claim 1 wherein said indicator dye is di-(3-sulfo-5-hydroxy-4-azaphenanthren-8- yl)7-carboxyphthalide.

11. A process of forming photographic diffusion transfer images whichcomprises, in combination, the steps of:

a. exposing a'photographic film unit which comprises a plurality oflayers including an opaque support layer carrying a photosensitivesilver halide layer having associated therewith a compound capable ofproviding as a function of development an imagewise distribution of animage-forming material which is processing composition soluble anddiffusible as a function of the point-to-point degree of exposure ofsaid silver halide layer and a diffusion transfer processimage-receiving layer adapted to receive solubilized image-formingmaterial diffusing thereto;

b. contacting said photosensitive silver halide layer with an aqueousalkaline processing composition to provide an indicator dye in a formcapable of absorbing a predetermined wavelength range of radiationactinic to said photosensitive material, said indicator dye beingselected from a 3,3- disubstituted phthalide and a 3,3-disubstitutednaphthalide wherein said 3,3 substituents, the same, are polycyclic arylradicals containing the group,

0H N: OH HN- ill I said radicals being bonded to said phthalide ornaphthalide by a carbon atom para to the -OH of said p;

c. effecting thereby development'of said silver halide emulsion;

d. forming thereby an imagewise distribution of diffusible image-formingmaterial, as a function of the point-to-point degree of emulsionexposure; and

e. transferring, by diffusion, at least a portion of said imagewisedistribution of diffusible image-forming material to said layer adaptedto receive said material to provide an image therein; said indicator dyebeing present during development in a position and quantity effective toabsorb said wavelength range of actinic radiation in an amountsufficient to prevent any substantial decrease, as a result ofperforming said process in the presence of incident actinic light withinsaid wavelength range, in the maximum density of the image obtained bythe transfer of said diffusible image-forming material.

12. A process of forming transfer images as defined in claim 11 whereinsaid indicator dye is disposed, at a pH below its pKa, in a separateprocessing composition permeable layer and said photosensitive silverhalide layer is positioned intermediate said opaque support and saidlayer containing said indicator dye.

13. A process of forming transfer images in color which comprises, incombination, the steps of:

a. exposing a photographic film unit which is adapted to be processed byapplication of pressure to release and distribute a processingcomposition and which includes, in combination, a photosensitive elementcomprising a composite structure containing, as essential layers, insequence, a first support layer opaque to incident actinic radiation; aphotosensitive silver halide layer having associated therewith acompound capable of providing as a function of development an imagewisedistribution of a dye image-forming material which is processingcomposition soluble and diffusible as a function of exposure of thephotosensitive silver halide layer to actinic radiation; a polymericlayer dyeable by said dye image-forming material; a second support layertransparent to incident actinic radiation; and means securing saidlayers in substantially fixed relationship; means for interposing areflecting agent and an indicator dye capable of absorbing incidentradiation within a predetermined wavelength range actinic to saidphotosensitive layer at a pH above its pKa intermediate said dyeablepolymeric layer and said photosensitive silver halide layer andassociated dye image-forming material subsequent to orl l photoexposureof said film unit, said indicator dye being selected from a3,3-disubstituted phthalide and a 3,3-disubstituted naphthalide whereinsaid 3,3 substituents, the same, are polycyclic aryl radicals containingthe group,

ill I said radicals being bonded to said phthalide or naphthalide by acarbon atom para to the OH of said p;

a rupturable container retaining an aqueous alkaline processingcomposition possessing a pH above the pKa of said indicator dye fixedlypositioned and extending transverse a leading edge of saidphotosensitive element to effect unidirectional discharge of thecontainers processing composition intermediate said dyeable polymericlayer and the photosensitive silver halide layer next adjacent theretoupon application of compressive force to said container;

b. applying compressive force to said rupturable container to effectunidirectional discharge of the containers processing compositionintermediate said dyeable polymeric layer and said photosensitive silverhalide layer;

c. effecting thereby substantial development of said silver halide layerand disposition of said reflecting agent and said indicator dye at a pHabove its pK-a intermediate said dyeable polymeric layer and saidphotosensitive silver halide layer;

d. as a result of said development, forming an imagewise distribution ofdiffusible dye image-forming material, as a function of thepoint-to-point degree of exposure of said photosensitive layer;

e. transferring, by diffusion, at least a portion of said imagewisedistribution of diffusible dye imageforming material to said dyeablepolymeric layer to provide a dye image thereto; and

f. maintaining said composite structure intact subsequent to saidprocessing, said indicator dye being present in a quantity effective toabsorb said wavelength range ofincident radiation in an amountsufficient in combination with said reflecting agent, to prevent anysubstantial decrease, as a result of performing said process in thepresence of incident actinic light within said wavelength range, in themaximum density of the image obtained by the transfer of said diffusibleimage-formingmaterial.

14. A process of forming transfer images in color as defined in claim 13wherein said indicator dye is initially disposed at a pH below its pKain an aqueous alkaline processing composition permeable layer of saidphotosensitive element intermediate said dyeable polymeric layer andsaid silver halide layer, and said rupturable container containing saidaqueous alkaline processing composition possessing a pH above the pKa ofsaid indicator dye is fixedly positioned and extends transverse aleading edge of said photosensitive element to effect unidirectionaldischarge of the processing composition intermediate said dyeablepolymeric layer and said layer containing said indicator dye uponapplication of compressive force to said container and including thestep of discharging said processing composition, subsequent to exposureof said photosensitive element, intermediate said dyeable polymericlayer and said layer containing said indicator dye.

15. A process of forming transfer images in color as defined in claim 13wherein said reflecting agent is tita nium dioxide and said indicatordye and said titanium dioxide are initially disposed in said aqueousalkaline processing composition as retained in said rupturablecontainer.

16. A process of forming transfer images in color as defined in claim 13wherein said photosensitive element includes at least one acid reactingpolymeric layer positioned intermediate at least one of (a) said firstopaque layer and the photosensitive silver halide layer next adjacentthereto, and (b) said second transparent layer and the dyeable polymericlayer next adjcaent thereto, and contains sufficient acidifying functionto effect reduction of said aqueous alkaline processing composition froma pH above to a pH below the pKa of said indicator dye and including thestep of transferring, by diffusion, subsequent to substantial transferdye image formation, a sufficient portion of the ions of said processingcomposition to said polymeric acid layer to thereby reduce said pH to apH below said pKa.

17. A process of forming transfer images in color as defined in claim 16wherein said dye-image forming material comprises a dye which is asilver halide developing agent and said photosensitive layer is a silverhalide emulsion.

18. A process of forming transfer images in color as defined in claim 17wherein said photosensitive element comprises at least two selectivelysensitized silver halide emulsion layers, each of said layers havingassociated therewith an image-forming dye, which is a silver halidedeveloping agent, of predetermined color, and is soluble and diffusible,in aqueous alkaline processing composition as a function of thepoint-to-point degree of exposure of the respective emulsion associatedtherewith.

19. A process of forming transfer images in color as defined in claim 13wherein said photosensitive element comprises three selectivelysensitized silver halide emulsion layers on said support, in sequence, ared sensitive silver halide emulsion layer having associated therewith acyan image-forming dye; a green-sensitive silver halide emulsion layerhaving associated therewith a magenta image-forming dye; ablue-sensitive silver halide emulsion layer having associated therewitha yellow image-forming dye; each of said cyan, magenta and yellowimage-forming dyes being silver halide developing agents and soluble anddiffusible in said aqueous alkaline processing solution.

20. A process as defined in claim 13 wherein said radicals of saidindicator dye contain the group,

OH N:

24. A process as defined in claim 13 wherein said indicator dye isdi-(3-sulfo-5-hydroxy-4-azaphenanthren- 8-yl)7-carboxyphthalide.

25. A photographic film unit which comprises a pluarlity of layersincluding a support layer carrying on one surface, in order, a layer ofphotosensitive material and a layer comprising an indicator dye disposedat a pH below its pKa selected from a 3,3-disubstituted phthalide and a3,3-disubstituted naphthalide wherein said 3,3 substituents, the same,are polycyclic aryl radicals containing the group,

OH HN- ill I said radicals being bonded to said phthalide or naphthalideby carbon atom para to the -OH of said group.

26. A photographic film unit as defined in claim wherein saidphotosensitive material is silver halide.

27. A photographic film unit as defined in claim 26 wherein said silverhalide layer has associated therewith a silver halide developing agent.

28. A photographic film unit as defined in claim 26 wherein said silverhalide layer has associated therewith a dye-providing compound capableof providing as a function of development an imagewise distribution of adye image-forming material which is processing composition soluble anddiffusible as a function of the point-to-point degree of exposure ofsaid silver halide layer.

29. A photographic film unit as defined in claim 28 which is adapted tobe processed by application of pressure to release and distribute aprocessing composition and which comprises, in combination:

a photosensitive element including a composite structure containing, asessential layers, in sequence, a first support layer opaque to incidentactinic radiation; at least two selectively sensitized silver halidelayers, each having associated therewith an image-forming dye which is asilver halide developing agent of predetermined color, each of said dyesbeing soluble and diffusible in alkaline processing composition as afunction of the pointto-point degree of exposure of the respectivesilver halide associated therewith, a polymeric layer dyeable by saiddye; a second support layer transparent to incident actinic radiation;and means securing said layers in substantially fixed relationship;

a rupturable container retaining an alkaline processing compositioncontaining reflecting agent fixedly positioned and extending transversea leading edge of said photosensitive element to effect unidirectionaldischarge of said containers processing composition between said dyeablepolymeric layer and the photosensitive silver halide layer next adjacentthereto upon application of pressure to said container; and an indicatordye capable of absorbing incident radiation within a predeterminedwavelength range actinic to said silver halide disposed in at least oneof said processing composition and, at a pH below its pKa, in a layerintermediate said photosensitive silver halide layer and said secondsupport layer transparent to incident actinic radiation, said indicatordye being selected from a 3,3-disubstituted phthalide and a3,3-disubstituted naphthalide wherein said 3,3 substituents, the

said radicals being bonded to said phthalide or naphthalide by a carbonatom para to the OH of said group.

30. A photographic film unit as defined in claim 29 including at leastone acid reacting polymeric layer positioned intermediate at least oneof said first opaque layer and the photosensitive silver halide layernext adjacent thereto, and said second transparent layer and the dyeablepolymeric layer next adjacent thereto, said polymeric acid layercontaining sufiicient acidifying function to effect reduction of saidprocessing composition from a first pH at which said image-forming dyeis substantially soluble and diffusible to a second pH at which saidimage-forming dye is substantially nondiffusible.

31. A photographic film unit as defined in claim 30 wherein saidreflecting agent taken together with said indicator dye are adapted toprevent further exposure of the selectively exposed silver halide layerduring processing in the presence of radiation within said predeterminedwavelength range actinic to the silver halide layer and incident on thesurface of the film unit opposite to the opaque support layer.

32. A photographic film unit as defined in claim 31 wherein saidphotosensitive element includes, as essential layers, in sequence, fromsaid opaque support layer, an alkaline solution permeable polymericlayer containing a cyan dye; a red-sensitive silver halide emulsionlayer; an alkaline solution permeable polymeric layer containing amagenta dye; a green-sensitive silver halide emulsion layer; an alkalinesolution permeable polymeric layer containing a yellow dye; a bluesensitive silver halide emulsion layer, each of said cyan, magenta andyellow dyes being silver halide developing agents and being soluble anddiffusible, in aqueous alkaline solution at said first pH andsubstantially insoluble in aqueous alkaline solution at said second pH.

33. A film unit as defined in claim 29 wherein said radicals of saidindicator dye contain the group;

on N:

34. A film unit as defined in claim 33 wherein said radicals areS-hydroxy-4-azaphenanthren-8-yl.

35. A film unit as defined in claim 34 wherein said dye is a phthalide.

36. A film unit as defined in claim 29 wherein said indicator dye isdi-(5-hydroxy-4-azaphenanthren-8-yl)7- carboxyphthalide.

37. A film unit as defined in claim 29 wherein said indicator dye isdi-3-sulfo-5-hydroxy-4-azaphenanthren- 8-yl) 7-carboxyphthalide.

38. A photographic processing composition comprising an aqueous alkalinesolution of a viscosity imparting reagent, a light-reflecting agent andan indicator dye selected from a 3,3-disubstituted phthalide and a3,3-clisubstituted naphthalide wherein said 3,3 substituents, the same,are polycyclic aryl radicals containing the group,

OH HN- OH N: M

law/K I said radicals being bonded to said phthalide or naphthalide by acarbon atom para to the OH of said group.

39. A photographic processing composition as defined in claim 38 whichadditionally contains a silver halide developing agent.

40. A composition as defined in claim 38 wherein said radicals of saidindicator dye contain the group,

of said indicator dye.

2. A process as defined in claim 1 wherein said Indicator dye isinitially disposed in said processing composition having a pH at whichsaid indicator dye is light-absorbing, said processing composition beingapplied to said photosensitive layer and said composition containingsaid indicator dye being separated from the photosensitive layersubsequent to substantial image development.
 3. A process as defined inclaim 1 wherein said indicator dye is retained in said element and isrendered ineffective to prevent viewing of the final image subsequent tosubstantial image development by adjusting the pH of said indicator dyesenvironment to a value at which it is substantially non-light-absorbing.4. A process as defined in claim 3 wherein said indicator dye isinitially present in a processing composition permeable layer at a pHvalue at which it is substantially non-light absorbing, said layer beingcoextensive with at least one surface of said photosensitive layer andsaid processing composition applied thereto having a pH at which saidindicator dye is light-absorbing.
 5. A process as defined in claim 1wherein said layer of photosensitive material is a silver halide layer.6. A process as defined in claim 1 wherein said radicals of saidindicator dye contain the group
 7. A process as defined in claim 6wherein said radicals are 5-hydroxy-4-azaphenanthren-8-yl.
 8. A processas defined in claim 7 wehrein said dye is a phthalide.
 9. A process asdefined in claim 1 wherein said indicator dye isdi-(5-hydroxy-4-azaphenanthren-8-yl)7-carboxyphthalide.
 10. A process asdefined in claim 1 wherein said indicator dye isdi-(3-sulfo-5-hydroxy-4-azaphenanthren-8-yl)7-carboxyphthalide.
 11. Aprocess of forming photographic diffusion transfer images whichcomprises, in combination, the steps of: a. exposing a photographic filmunit which comprises a plurality of layers including an opaque supportlayer carrying a photosensitive silver halide layer having associatedtherewith a compound capable of providing as a function of developmentan imagewise distribution of an image-forming material which isprocessing composition soluble and diffusible as a function of thepoint-to-point degree of exposure of said silver halide layer and adiffusion transfer process image-receiving layer adapted to receivesolubilized image-forming material diffusing thereto; b. contacting saidphotosensitive silver halide layer with an aqueous alkaline processingcomposition to provide an indicator dye in a form capable of absorbing apredetermined wavelength range of radiation actinic to saidphotosensitive material, said indicator dye being selected from a3,3-disubstituted phthalide and a 3,3-disubstituted naphthalide whereinsaid 3,3 substituents, the same, are polycyclic aryl radicals containingthe group,
 12. A process of forming transfer images as defined in claim11 wherein said indicator dye is disposed, at a pH below its pKa, in aseparate processinG composition permeable layer and said photosensitivesilver halide layer is positioned intermediate said opaque support andsaid layer containing said indicator dye.
 13. A process of formingtransfer images in color which comprises, in combination, the steps of:a. exposing a photographic film unit which is adapted to be processed byapplication of pressure to release and distribute a processingcomposition and which includes, in combination, a photosensitive elementcomprising a composite structure containing, as essential layers, insequence, a first support layer opaque to incident actinic radiation; aphotosensitive silver halide layer having associated therewith acompound capable of providing as a function of development an imagewisedistribution of a dye image-forming material which is processingcomposition soluble and diffusible as a function of exposure of thephotosensitive silver halide layer to actinic radiation; a polymericlayer dyeable by said dye image-forming material; a second support layertransparent to incident actinic radiation; and means securing saidlayers in substantially fixed relationship; means for interposing areflecting agent and an indicator dye capable of absorbing incidentradiation within a predetermined wavelength range actinic to saidphotosensitive layer at a pH above its pKa intermediate said dyeablepolymeric layer and said photosensitive silver halide layer andassociated dye image-forming material subsequent to photoexposure ofsaid film unit, said indicator dye being selected from a3,3-disubstituted phthalide and a 3,3-disubstituted naphthalide whereinsaid 3,3 substituents, the same, are polycyclic aryl radicals containingthe group,
 14. A process of forming transfer images in color as definedin claim 13 wherein said indicator dye is initially disposed at a pHbelow its pKa in an aqueous alkaline processing composition permeablelayer of said photosensitive element intermediate said dyeable polymericlayer and said silver halide layer, and said rupturable containercontaining said aqueous alkaline processing composition possessing a pHabove the pKa of said indicator dye is fixedly positioned and extendstransverse a leading edge of said photosensitive element to effectunidirectional discharge of the processing composition intermediate saiddyeable polymeric layer and said layer containing said indicator dyeupon application of compressive force to said container and includingthe step of discharging said processing composition, subsequent toexposure of said photosensitive element, intermediate said dyeablepolymeric layer and said layer containing said indicator dye.
 15. Aprocess of forming transfer images in color as defined in claim 13wherein said reflecting agent is titanium dioxide and said indicator dyeand said titanium dioxide are initially disposed in said aqueousalkaline processing composition as retained in said rupturablecontainer.
 16. A process of forming transfer images in color as definedin claim 13 wherein said photosensitive element includes at least oneacid reacting polymeric layer positioned intermediate at least one of(a) said first opaque layer and the photosensitive silver halide layernext adjacent thereto, and (b) said second transparent layer and thedyeable polymeric layer next adjcaent thereto, and contains sufficientacidifying function to effect reduction of said aqueous alkalineprocessing composition from a pH above to a pH below the pKa of saidindicator dye and including the step of transferring, by diffusion,subsequent to substantial transfer dye image formation, a sufficientportion of the ions of said processing composition to said polymericacid layer to thereby reduce said pH to a pH below said pKa.
 17. Aprocess of forming transfer images in color as defined in claim 16wherein said dye-image forming material comprises a dye which is asilver halide developing agent and said photosensitive layer is a silverhalide emulsion.
 18. A process of forming transfer images in color asdefined in claim 17 wherein said photosensitive element comprises atleast two selectively sensitized silver halide emulsion layers, each ofsaid layers having associated therewith an image-forming dye, which is asilver halide developing agent, of predetermined color, and is solubleand diffusible, in aqueous alkaline processing composition as a functionof the point-to-point degree of exposure of the respective emulsionassociated therewith.
 19. A process of forming transfer images in coloras defined in claim 13 wherein said photosensitive element comprisesthree selectively sensitized silver halide emulsion layers on saidsupport, in sequence, a red-sensitive silver halide emulsion layerhaving associated therewith a cyan image-forming dye; a green-sensitivesilver halide emulsion layer having associated therewith a magentaimage-forming dye; a blue-sensitive silver halide emulsion layer havingassociated therewith a yellow image-forming dye; each of said cyan,magenta and yellow image-forming dyes being silver halide developingagents and soluble and diffusible in said aqueous alkaline processingsolution.
 20. A process as defined in claim 13 wherein said radicals ofsaid indicator dye contain the group,
 21. A process as defined in claim20 wherein said radicals are 5-hydroxy-4-azaphenanthren-8-yl.
 22. Aprocess as defined in claim 21 wherein said dye is a phthalide.
 23. Aprocess as defined in claim 13 wherein said indicator dye isdi-(5-hydroxy-4-azaphenanthren-8-yl)7-carboxyphthalide.
 24. A process asdefined in claim 13 wherein said indicator dye isdi-(3-sulfo-5-hydroxy-4-azaphenanthren-8-yl)7-carboxyphthalide.
 25. Aphotographic film unit which comprises a pluarlity of layers including asupport layer carrying on one surface, in order, a layer ofphotosensitive material and a layer comprising an indicator dye disposedat a pH below its pKa sElected from a 3,3-disubstituted phthalide and a3,3-disubstituted naphthalide wherein said 3,3 substituents, the same,are polycyclic aryl radicals containing the group,
 26. A photographicfilm unit as defined in claim 25 wherein said photosensitive material issilver halide.
 27. A photographic film unit as defined in claim 26wherein said silver halide layer has associated therewith a silverhalide developing agent.
 28. A photographic film unit as defined inclaim 26 wherein said silver halide layer has associated therewith adye-providing compound capable of providing as a function of developmentan imagewise distribution of a dye image-forming material which isprocessing composition soluble and diffusible as a function of thepoint-to-point degree of exposure of said silver halide layer.
 29. Aphotographic film unit as defined in claim 28 which is adapted to beprocessed by application of pressure to release and distribute aprocessing composition and which comprises, in combination: aphotosensitive element including a composite structure containing, asessential layers, in sequence, a first support layer opaque to incidentactinic radiation; at least two selectively sensitized silver halidelayers, each having associated therewith an image-forming dye which is asilver halide developing agent of predetermined color, each of said dyesbeing soluble and diffusible in alkaline processing composition as afunction of the point-to-point degree of exposure of the respectivesilver halide associated therewith, a polymeric layer dyeable by saiddye; a second support layer transparent to incident actinic radiation;and means securing said layers in substantially fixed relationship; arupturable container retaining an alkaline processing compositioncontaining reflecting agent fixedly positioned and extending transversea leading edge of said photosensitive element to effect unidirectionaldischarge of said container''s processing composition between saiddyeable polymeric layer and the photosensitive silver halide layer nextadjacent thereto upon application of pressure to said container; and anindicator dye capable of absorbing incident radiation within apredetermined wavelength range actinic to said silver halide disposed inat least one of said processing composition and, at a pH below its pKa,in a layer intermediate said photosensitive silver halide layer and saidsecond support layer transparent to incident actinic radiation, saidindicator dye being selected from a 3,3-disubstituted phthalide and a3,3-disubstituted naphthalide wherein said 3,3 substituents, the same,are polycyclic aryl radicals containing the group,
 30. A photographicfilm unit as defined in claim 29 including at least one acid reactingpolymeric layer positioned intermediate at least one of said firstopaque layer and the photosensitive silver halide layer next adjacentthereto, and said second transparent layer and the dyeable polymericlayer next adjacent thereto, said polymeric acid layer containingsufficient acidifying function to effect reduction of said processingcomposition from a first pH at which said image-forming dye issubstantially soluble and diffusible to a second pH at which saidimage-forming dye is substantially nondiffusible.
 31. A photographicfilm unit as defined in claim 30 wherein said reflecting agent takentogether with said indicator dye are adapted to prevent further exposureof the selectively exposed silver halide layer during processing in thepresence of radiation within said predetermined wavelength range actinicto the silver halide layer and incident on the surface of the film unitopposite to the opaque support layer.
 32. A photographic film unit Asdefined in claim 31 wherein said photosensitive element includes, asessential layers, in sequence, from said opaque support layer, analkaline solution permeable polymeric layer containing a cyan dye; ared-sensitive silver halide emulsion layer; an alkaline solutionpermeable polymeric layer containing a magenta dye; a green-sensitivesilver halide emulsion layer; an alkaline solution permeable polymericlayer containing a yellow dye; a blue-sensitive silver halide emulsionlayer, each of said cyan, magenta and yellow dyes being silver halidedeveloping agents and being soluble and diffusible, in aqueous alkalinesolution at said first pH and substantially insoluble in aqueousalkaline solution at said second pH.
 33. A film unit as defined in claim29 wherein said radicals of said indicator dye contain the group;
 34. Afilm unit as defined in claim 33 wherein said radicals are5-hydroxy-4-azaphenanthren-8-yl.
 35. A film unit as defined in claim 34wherein said dye is a phthalide.
 36. A film unit as defined in claim 29wherein said indicator dye isdi-(5-hydroxy-4-azaphenanthren-8-yl)7-carboxyphthalide.
 37. A film unitas defined in claim 29 wherein said indicator dye isdi-3-sulfo-5-hydroxy-4-azaphenanthren-8-yl) 7-carboxyphthalide.
 38. Aphotographic processing composition comprising an aqueous alkalinesolution of a viscosity imparting reagent, a light-reflecting agent andan indicator dye selected from a 3,3-disubstituted phthalide and a3,3-disubstituted naphthalide wherein said 3,3 substituents, the same,are polycyclic aryl radicals containing the group,
 39. A photographicprocessing composition as defined in claim 38 which additionallycontains a silver halide developing agent.
 40. A composition as definedin claim 38 wherein said radicals of said indicator dye contain thegroup,
 41. A composition as defined in claim 40 wherein said radicalsare 5-hydroxy-4-azaphenanthren-8-yl.
 42. A composition as defined inclaim 41 wherein said dye is a phthalide.
 43. A composition as definedin claim 38 wherein said indicator dye isdi-(5-hydroxy-4-azaphenanthren-8-yl)7-carboxyphthalide.
 44. Acomposition as defined in claim 38 wherein said indicator dye isdi-(3-sulfo-5-hydroxy-4-azaphenanthren-8-yl)7-carboxyphthalide.
 45. Acomposition as defined in claim 38 wherein said aqueous alkalinesolution has a pH above the pKa of said indicator dye.